This invention relates to laminated packaging materials for foodstuffs. More particularly, it relates to a laminated material suitable for use in flexible containers or pouches for foods such as potato chips, corn chips, cookies, and the like.
Flexible walled pouches, bags and similar containers have been used with satisfactory results, and to an increasing extent, in the packaging of products such as potato chips, corn chips, cookies and the like where it is essential that the freshness of the product be maintained for a number of months. Generally, such containers are prepared from multi-layered laminated packaging materials whose layers comprise polyolefin resin films and metallic foil. The packaging materials may have from 2 to 8 or more discrete layers, of which one or more layers may consist of adhesive material.
U.S. Pat. No. 3,616,190 discloses a laminated packaging material comprising--in order from the outer layer to the inner layer--cellophane, polyethylene, aluminum foil and heat-sealable polyethylene. The cellophane functions both as an outer layer and as a decorative surface, the decorative design being printed in reverse on the inner side of the cellophane sheet.
U.S. Pat. No. 4,096,309 discloses a laminate comprising a non-woven outer sheet of spun-bonded polymer such as polyethylene, polypropylene or polyester. The next adjacent layer can be a polyolefin film such as polyethylene or polypropylene. The next adjacent layer is a metallic foil and the innermost layer is a heat-sealable polyolefin such as polyethylene or polypropylene. As an outer surface layer, there is preferably provided a face ply of a smooth, nonporous material, such as kraft paper.
U.S. Pat. No. 4,190,477 discloses a laminate of (1) polyester or nylon, (2) metallic foil, (3) extrusiongrade propylene polymer or copolymer and (4) a sealant layer of polypropylene, polyethylene or ethylene vinyl acetate.
U.S. Pat. No. 4,309,466 discloses a flexible laminated packaging material comprising, from the outside in, (1) a biaxially-oriented thermoplastic material such as nylon or polypropylene, (2) a metallized thermoplastic material such as a polyester or polypropylene, and (3) a heat-sealable polyolefin. Layer (2) is metallized by vacuum deposition of metal, preferably aluminum particles. Either layer (1) or layer (2) is provided with a coating of poly (vinylidene chloride).
U.S. Pat. No. 4,363,841 discloses a laminate of (1) an outer transparent sheet of nylon, polyester, cellophane or polypropylene, (2) a co-extruded layer of pigmented polyethylene and ethylene acrylic acid copolymer, (3) a metallic foil, preferably aluminum, and (4) a heat-sealable polyolefin as the inner-most layer.
In the packaging of foodstuffs such as potato chips, cookies, and the like, the packages are generally imprinted on the outermost layer of a laminate from which the package is made. When the outermost layer is transparent, the printing thereon is often difficult to discern, particularly, if the package contents do not provide sufficient contrast between the lettering and its background. Thus, printing is generally effected in reverse on the inner surface of the outer transparent layer (1) of the laminate as disclosed in U.S. Pat. No. 4,363,841. The pigmented polyethylene in co-extruded layer (2) provides a suitable contrasting background to the imprinted outermost layer. The ethylene acrylic acid copolymer in layer (2) provides a strong bond to the metallic foil. However, when the upper-most layer is a transparent nylon, the bond strength between this layer and the pigmented polyethylene has been less than optimal.
It is therefore a principal object of this invention to provide a metal-containing laminated packaging material having an outer layer of nylon and an inner, adjacent layer comprising pigmented polyethylene, said packaging material exhibiting an improved bond strength.